Background and Summary of the Invention
1. Technical Field
This invention relates to multiplexers, and more particularly to a multioctave printed multiplexer having a plurality of independent channels coupled at their inputs to a common input junction.
2. Background
Satellites and many avionic systems require broad band arrays to perform functions such as electronic beam steering, target tracking and scan loss recovery. Signals from the array elements must typically be frequency-multiplexed into suboctave bands before weighting and combining in a beam forming network. It is therefore important that the multiplexers be not only wide band, but also small and low cost to make them suitable for mass production applications and applications where having a small physical size is highly desirable.
Current multiplexer technologies include conventional waveguide, combline and suspended substrate implementations. Each of these technologies, however, suffers from one or more drawbacks which limit their utility in satellite and avionic systems. Waveguide multiplexers are typically too bulky and have overall dimensions unsuitable for applications involving satellites and avionic systems. Moreover, waveguide multiplexers are suitable only for narrow band applications having frequency variations of typically less than 10 percent.
Combline multiplexers are relatively expensive to fabricate, assemble and test in large quantities. Such multiplexers are also undesirably bulky and typically have dimensions making them less than desirable for satellite and avionic systems.
Suspended substrate technology generally uses a plurality of highpass and lowpass filters to extract desired bandwidths from each channel sequentially. However, the number of high pass and lowpass filters required to effect the desired degree of multiplexing, typically at least 5 to 6 such filters being required, results in a multiplexer having a larger size than what is ideally desired, in addition to higher inband RF signal loss. The generally high inband RF signal loss degrades the sensitivity of such multiplexers and further limits their utility in many satellite and avionic systems applications.
It is therefore a principal object of the present invention to provide a microwave multiplexer particularly well suited for satellite and avionic systems applications where the multiplexer is extremely compact and light in weight, as well as particularly well suited for low cost mass production.
It is further an object of the present invention to provide a multiplexer having a plurality of independent channels each having an input coupled to the inputs of each of the other channels and to a common input junction, to thereby reduce the number of highpass and lowpass filters required to effect the desired degree of multiplexing.
It is still a further object of the present invention to provide a common input junction, printed multioctave multiplexer which may be formed with either a suspended substrate or a microstrip. It is yet another object of the present invention to provide a common input junction, printed multioctave multiplexer which provides improved adjacent channel rejection at its crossover frequencies and reduced inband RF signal loss at each of its outputs.